Generally, a semi-automatic gear transmission for an automobile, which is capable of changing gears through automatic engagement or disengagement of a clutch without using a clutch pedal is provided with a fluid coupling interposed between an engine and the gear transmission to thereby absorb a shock caused by the clutch engagement so that power from the engine may be transmitted to the gear transmission by way of the fluid coupling and clutch. The fluid coupling, clutch, and gear transmission, which are disposed in alignment on the axis of the output shaft of the engine, are housed within one housing and assembled integrally with the engine. These three units together with a differential gear unit having a drive shaft, constitute a power unit. The power unit is mounted in an engine compartment at the front or rear of the automobile in either a transverse or longitudinal position so that the axis of the output shaft extends widthwise or longitudinally of the car-body.
The aforesaid power transmission usually has a partition between the fluid coupling and the clutch, the partition carrying one axial end of an intermediate shaft, a free end of the output shaft of the gear transmission, and a boss of a pump at the fluid coupling, where a turbine thereof and a clutch wheel at the clutch are connected with the intermediate shaft.
The provision of the partition within the housing increases the axial length of the power transmission as a whole due to the aligned arrangement of the fluid coupling, clutch, and gear transmission. Especially in, a front-engine front-drive type automobile, when the engine is transversely mounted, the width of the engine compartment is limited causing difficulty as the engine room is too small to accommodate the power unit.
On the other hand, the oil circulation type fluid coupling uses as operating oil a part of lubricating oil supplied under pressure to each engine unit by means of an oil pump, and the oil, after use as operating oil, is returned from the fluid coupling into the engine. Passageways, through which the oil is supplied to or returned from the fluid coupling, are formed partially at the partition and open therethrough to the exterior of the housing, the openings of the passageways being connected with oil pipes so that the passageways communicate with the interior of the engine.
One problem with this arrangement is the oil passageways are complicated in construction and use of the oil pipes increases the number of required parts. Furthermore, there is a possibility of not only a breakdown at the oil pipes but also leakage of the lubricating oil caused by a broken pipe, resulting in damage to the engine or poor transmission of power due to a shortage of lubricating oil.